This invention relates generally to injection molding and more particularly to an improved heated manifold system for conveying pressurized melt from a single inlet to a number of spaced outlets each leading to a different cavity.
Multi-cavity injection molding is well known. Often the cavities are arranged in a row with a single elongated manifold conveying melt to a nozzle or probe leading to each of them. An example of this type of arrangement is shown in FIG. 1 of the applicant's U.S. patent application Ser. No. 725,799 filed Apr. 22, 1985 entitled "Composite Plate Method of Manufacturing Injection Molding Manifold" now U.S. Pat. No. 4,648,546 which is herein incorporated by reference. The cavities and manifold can also be arranged in an H or X shaped configuration and an example of this is shown in the applicant's U.S. Pat. No. 4,439,915 which issued Apr. 3, 1984 entitled "Heater Installation in Molding Members".
It is also known to form injection molding manifold systems of a number of interconnectable units rather than an integral system to provide more flexibiltiy in design. An example of this is shown in EWIKON Brochure 01799 entitled "Heisskanalsystem", although this discloses a type of "cold" manifold arrangement wherein the heating element is located in the melt passage itself rather than in the body of the manifold.
Reliability and speed of operation are, of course, very critical to the successful operation of this type of injection molding system. Therefore, it is very desirable that the volume of flow of melt through the branches of the hot runner passage be uniform with a minimal pressure drop regardless of the location of the various cavities relative to the inlet. It will be appreciated that this becomes more difficult as the number of cavities is increased to meet volume requirements.